How many significant figures does $0.0100$ have?
Explanation: Identify the non-zero digits and any zeros between them. These are all significant. $0.0{1}00$ Leading zeros are not significant. $\color{orange}{0.0}{1}00$ Since there is a decimal, trailing zeros are significant. $\color{orange}{0.0}{100}$ Counting all the significant digits gives us 3.